1. Field of the Invention
This invention relates to an electroluminescent device, more particularly to an electroluminescent device including at least one moisture barrier layer having inorganic films and optionally at least one polymer film interposed between two of the inorganic films.
2. Description of the Related Art
U.S. Pat. No. 7,733,008 discloses an organic light emitting diode (OLED) that includes a substrate, an anode formed on the substrate, a first moisture barrier layer formed on the anode, a hole transport layer formed on the first moisture barrier layer, an electroluminescent layer formed on the hole transport layer, a second moisture barrier layer formed on the electroluminescent layer, a cathode formed on the second moisture barrier layer, and an encapsulation layer encapsulating at least partially all of these layers. The thickness of the first and second moisture barrier layers ranges from 1 nm to 20 nm. The first and second moisture barrier layers are made from a polymer selected from polyimide, TEFLON®, and parylene, and have a water vapor transmission rate (WVTR) ranging from 0.1 g/m2/day to 50 g/m2/day at 95% RH (Relative Humidity) and 39° C.
U.S. Pat. No. 7,220,687 discloses an OLED that includes a substrate, an anode formed on the substrate, an organic polymer material layer formed on the anode and having a hole transport film and an emissive film, a cathode formed on the organic polymer material layer, and an encapsulation layer deposited on the cathode. The thickness of the encapsulation layer ranges from 50 nm to 2000 nm. The encapsulation layer can be made from silicon nitride (Si3N4), silicon dioxide (SiO2), or silicon oxynitride (SiOxNy). Formation of the encapsulation layer is performed by introducing precursor sources together with hydrogen into a deposition chamber during chemical vapor deposition. The introduction of hydrogen into the deposition chamber can improve the WVTR of the encapsulation layer thus formed from about 1×10−2 g/m2/day (without hydrogen) to about a range between 1×10−3 g/m2/day and 1×10−4 g/m2/day (with hydrogen) at 90% RH and 38° C. Although the use of hydrogen can reduce the WVTR of the encapsulation layer, the manufacturing costs of the OLED may be considerably increased due to the use of hydrogen in the manufacturing process.